[BUILD] 1176LN Rev D DIY
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Echo North
Well-known member
RichardM said:
You have that much DC there? What is the AC?
Echo North
Well-known member
RichardM said:
You need to check your voltages, specifically in the signal amp.
http://mnats.net/files/1176REVD_VOLTS.pdf
benlindell
Well-known member
bump, just wondering if anyone has any ideas as to what might be causing the drop on my -10 rail?benlindell said:
rockmonkey731
Member
Hey everyone, I posted this in a different thread but I figure this would be a better place.
Whenever I turn my rev D on, the fuse blows. I've upgraded to a 500mA slow-blo, and it still blows. I can't find any wires/solders touching, so i don't think it's a short issue. I need to test my components, and I'm wondering if I can test them while still in the pcb, or do I need to take out all the stuff I check?
Thanks.
EDIT: I turned it on and the fuse didn't blow, I know it's not calibrated, but the meter showed -infinity on GR, -10 on +8, and about -7 on +4. I turned the unit off, and C25 blew. It smoked and everything. It happened exactly when I turned the unit off, but the fuse never blew. I have no idea what could be going on, or what would make c25 blow when I turn off the unit.
Whenever I turn my rev D on, the fuse blows. I've upgraded to a 500mA slow-blo, and it still blows. I can't find any wires/solders touching, so i don't think it's a short issue. I need to test my components, and I'm wondering if I can test them while still in the pcb, or do I need to take out all the stuff I check?
Thanks.
EDIT: I turned it on and the fuse didn't blow, I know it's not calibrated, but the meter showed -infinity on GR, -10 on +8, and about -7 on +4. I turned the unit off, and C25 blew. It smoked and everything. It happened exactly when I turned the unit off, but the fuse never blew. I have no idea what could be going on, or what would make c25 blow when I turn off the unit.
Harpo
Well-known member
Clean the board from electrolyte that came out of C25 (and be more specific whatever 'everything' else might be) and replace C25 and the probably blown diodes CR7 and CR8 (or double check polarity of CR7 and CR8 and if they are still diodes after C25 failed. These 1N400x can only take 1A and might have failed short). You fitted at least 50V rated caps for C25 and C26 with correct parts orientation ?rockmonkey731 said:
rockmonkey731
Member
The seals at the top separated, and smoke/steam came out of the top for about a second. The polarity was correct, and it was the 2200uF 50v cap included in the mouser cart.
benlindell
Well-known member
Can someone with a working unit check out the voltages on the left side of CR7, CR8, CR9, CR10. I'm getting +32Vdc from CR7 and CR8. I'm getting -25Vdc from CR9 and CR10 but also 11Vac, are these normal?
I have gone through and tested everything. I have found that my GR METER DRIVER section is all down about 2 vdc. I think the culprits might be r66, r72 and possibly r79. I am going to replace all of these when I get some new parts from mouser. Am I on the right track? Could low voltage in this area be the cause of no input in the unit? Thanks!
Rich
Rich
rokus666
Well-known member
By the way,
My second build was super easy and super fast. Thanks to all your help troubleshooting on the first one. Mnats' instructions are really idiot proof, you can't miss it if you attentively follow.
Great job once again, I have now two 1176 compressors. Time to move on to something else...
My second build was super easy and super fast. Thanks to all your help troubleshooting on the first one. Mnats' instructions are really idiot proof, you can't miss it if you attentively follow.
Great job once again, I have now two 1176 compressors. Time to move on to something else...
Echo North
Well-known member
Hey Ben,
I've got +40DC and +30DC w/ 8VAC.
Mike
I've got +40DC and +30DC w/ 8VAC.
Mike
benlindell said:
Echo North
Well-known member
RichardM said:
No it shouldn't.
What is your DC at the Q11 gate?
Echo North
Well-known member
RichardM said:
8.7 VDC is your gate voltage?!?!
This should be a smaller - DCV.
Echo North
Well-known member
RichardM said:
Seems like it could be a little low. Were you ever able to set your Qbias?
I wasn't able to get the q bias set but I will try again. Is there anything special that I should do with all of the little trimmer pots before starting or is it only the Qbias trimmer that is in play for this? I did get the correct reading at the input xlr but no reading at the out put. By the way,thanks again for all of your help.
Rich
Rich
Echo North
Well-known member
RichardM said:
The voltages in the meter section on the voltage guide are dependent on the unit being calibrated correctly.
Right now if you can't pass audio, let's tackle that first. Set you qbias to -2 VDC or more by placing your DC volt meter between the Q1 gate and ground. Now turn your GR off by setting the attack to "off". The should effectively disable all GR and Q1 turning your 1176 into a 2 stage mic pre with about 40 dB of gain.
If you're not getting any output like this, there is an issue in you preamp stages. Feed a 1khz 1VAC signal into the input and set the in/out knobs to the middle. Now let's see where the signal dies.
Measure the AC voltage at these points using GROUND as the reference.
1. Input XLR pin 2
2. + input at the PCB (by C1)
3. - of C7
4. Output XLR pin 2
